1. Field of the Invention
The invention relates a method of fabricating metallization, and more particularly to a method of fabricating self-align metal nitride for copper passivation which can prevent short circuit between metal layers.
2. Description of the Related Art
FIG. 1 is a cross-sectional view of a structure of a conventional metallization. A substrate 100 having devices is provided and a dielectric layer 102 such as oxide is formed on the substrate 100. An opening is defined within the dielectric layer 102 and filled with a metal layer 104. In addition, a barrier layer 106 is formed on the opening. When copper is used as metal layer, copper will diffuse into the dielectric layer 102 when CVD is performed at a general temperature. Therefore a barrier layer 106 such as tantalum nitride (TaN) or tungsten nitride (WN) should be formed at the interface of dielectric layer 102 and copper 104. Diffusion from copper can be prevented by the barrier layer 106. In the conventional damascene process, an inter-metal dielectrics 108 is formed on the dielectric layer 102 after a planarization process is performed by chemical mechanical polishing (CMP). Metallization, for example, a metal plug 110 or a trench (not shown) is formed within the inter-metal dielectrics 108. However, there is no barrier layer formed on the upper surface of the metal line 104 to prevent diffusion of the copper as the deposition proceeds. So short circuit is produced by the dielectric layer 102 and inter-metal dielectrics 108 and the reliability of device decreases.